Showing papers by "University of Bordeaux published in 1989"

Factors that predict individual vulnerability to amphetamine self-administration

Abstract: Clinical observations show that there is considerable individual variability in the response to the addictive properties of drugs. This individual variability needs to be taken into account in animal models of addiction. Like humans, only some rats readily self-administer low doses of psychostimulants. The individual animals at risk can be identified on the basis of their response to environmental or pharmacological challenges. This predisposition to develop self-administration can be induced by repeated treatment with amphetamine. These results may help elucidate the neurobiological basis of addiction liability observed in both rats and humans.

Heaps of Pieces, I: Basic Definitions and Combinatorial Lemmas

Abstract: We introduce the combinatorial notion of heaps of pieces, which gives a geometric interpretation of the Cartier-Foata's commutation monoid. This theory unifies and simplifies many other works in Combinatorics : bijective proofs in matrix algebra (MacMahon Master theorem, inversion matrix formula, Jacobi identity, Cayley-Hamilton theorem), combinatorial theory for general (formal) orthogonal polynomials, reciprocal of Rogers-Ramanujan identities, graph theory (matching and chromatic polynomials). Heaps may bring new light on classical subjects as poset theory. They are related to other fields as Theoretical Computer Science (parallelism) and Statistical Physics (directed animals problem, lattice gas model with hard-core interactions). Complete proofs and definitions are given in sections 2, 3,4,5. Other sections give a summary of possible applications of heaps.

A Middle Palaeolithic human hyoid bone

Abstract: The origin of human language, and in particular the question of whether or not Neanderthal man was capable of language/speech, is of major interest to anthropologists but remains an area of great controversy. Despite palaeoneurological evidence to the contrary, many researchers hold to the view that Neanderthals were incapable of language/speech, basing their arguments largely on studies of laryngeal/basicranial morphology. Studies, however, have been hampered by the absence of unambiguous fossil evidence. We now report the discovery of a well-preserved human hyoid bone from Middle Palaeolithic layers of Kebara Cave, Mount Carmel, Israel, dating from about 60,000 years BP. The bone is almost identical in size and shape to the hyoid of present-day populations, suggesting that there has been little or no change in the visceral skeleton (including the hyoid, middle ear ossicles, and inferentially the larynx) during the past 60,000 years of human evolution. We conclude that the morphological basis for human speech capability appears to have been fully developed during the Middle Palaeolithic.

Switching of a Neuron from One Network to Another by Sensory-Induced Changes in Membrane Properties

Abstract: A neuron that is an integral member of the pyloric neural network of the lobster stomatogastric nervous system leaves this network and instead fires exclusively with another stomatogastric nervous system network, the cardiac sac network, whenever the cardiac sac network is active. This switch is associated with the neuron losing, in a long-lasting fashion, regenerative oscillatory membrane properties that underlie its participation in the pyloric network. Functional membership of neurons in central networks is thus not fixed, and long-lasting neuromodulatory influences, controlled at least in part by sensory inputs, can switch neurons from one network to another.

Influence of seagrass beds and oyster parks on the abundance and biomass patterns of meio- and macrobenthos in tidal flats

Abstract: In Arcachon Bay, on the south-west coast of France, the intertidal area is mainly occupied by sandbanks, oyster parks (Crassostrea gigas) and mud flats covered with seagrass beds (Zostera noltii). In order to estimate the relative contribution of meio- and macrofauna to the benthic ecology of these tidal flats, seven stations were studied seasonally for a year. Relationships between faunal density and biomass, and external factors such as sediment structure, benthic chlorophyll and seagrass debris were investigated. A comparison was made between bare sands, oyster beds and vegetated sediment in semi-exposed conditions and in sheltered areas. Using a stepwise method of multiple linear regression it was shown that high densities of macrobenthos are mostly explained by high quantities of plant debris. For meiofauna, together with plant debris, other effective variables are involved: silt content, organic carbon, chlorophyll pigments. On an average, a correlation between macro- and meiofaunal abundances could be found. However, this general pattern is modified by the biogenic structure created by the oysters and seagrass. When compared to the adjacent sandbanks, oysters clearly enhanced meiofaunal abundance (from 1130–4170 individuals 10 cm−2) but depressed macrofaunal densities (from 640-370 individuals 400 cm−2). The organic-rich oyster biodeposits probably favour meiofauna by an increase of the trophic resources but do not favour macroinfauna by inducing low oxygen concentrations. Moreover, it is likely that macrofauna is more sensitive to predation than meiofauna both in sandbanks and in oyster parks. For both meio- and macrofauna the highest incidences (7200 individuals 10 cm−2 and 2470 individuals 400 cm−2, respectively) are recorded in seagrass bed sediments. Zostera induces an enhancement of organic detritus and provides a refuge against predation. In terms of biomass, the macrofauna/meiofauna ratio is 25·1 in sandbanks, 1·5 in oyster parks and 4·2 in seagrass bed sediments. Macrofaunal biomass is more variable both spatially and temporally than meiofauna biomass. It is likely that the macrofauna is more sensitive to external factors such as predation, anoxia, exposure, than the meiofauna. Meiofauna abundance and biomass are more usually a function of food abundance and physical properties of the sediment.

Incidence and patterning of dental enamel hypoplasia among the Neandertals

Abstract: Dental enamel hypoplasia (DEH), as an indicator of nonspecific stress during development, provides an assessment of the relative morbidity of past human populations. An investigation of 669 Neandertal dental crowns yielded an overall DEH frequency of 36.0% by tooth (41.9% for permanent teeth; 3.9% for deciduous teeth) and about 75% by individual. These incidences place the Neandertals at the top of recent human ranges of variation in DEH frequencies, indicating high levels of stress during development. The paucity of deciduous tooth DEH and M1 DEH, combined with generally increasing levels of DEH through later calcifying teeth, suggests that the stress was primarily nutritional, beginning at weaning and continuing through adolescence. This supports paleontological and archeological interpretations implying significantly lower effectiveness for Neandertal foraging compared to that of modern humans.

Aminoglycoside antibiotics impair calcium entry but not viability and motility in isolated cochlear outer hair cells.

Abstract: Cochlear outer hair cells have been well established as primary targets of the ototoxic actions of aminoglycoside antibiotics. These cells, isolated from the guinea pig cochlea and maintained in short-term culture, were used as a model for evaluating the acute effects of gentamicin on cell viability, depolarization-induced transmembrane calcium flux, and depolarization-induced motile responses. On the basis of morphology and fluorochromasia, the presence of extracellular gentamicin as high as 5 mM did not affect the viability of the cells for up to 6 hr, the longest time tested. Viable cells showed binding of fluorescently tagged gentamicin to their base but excluded the drug from their cytoplasm. In response to [K+]-depolarization, intracellular calcium levels (monitored with the fluorescent calcium-sensitive dye fluo-3) increased from a resting value of 218 ± 102 nM to 2,018 ± 1,077 nM concomitant with a cell shortening of 0.7% ± 1.3%. The depolarization-induced calcium increase was apparently caused by calcium entry into the cell as it was inhibited by the calcium-channel blocker methoxyverapamil and prevented in the absence of extracellular calcium. Both gentamicin and neomycin blocked the [K+]-induced calcium increase at an IC50 of 50 μM. Despite the inhibition of calcium entry the ability of the outer hair cells to shorten under [K+]-depolarization was not impaired; in fact, cell shortening was even more pronounced in the absence of calcium influx (2.6% ± 1.4%). This argues effectively against the existence of a calcium-dependent actomyosin-mediated component in [K+]-induced shape changes. The results suggest the existence of voltage-gated calcium channels in outer hair cells and that calcium influx through these channels is impaired by the aminoglycoside antibiotics neomycin and gentamicin. This action may be part of the acute ototoxic mechanism of these molecules. Furthermore, the results not only confirm the calcium independence of the depolarization-induced motility but also suggest that calcium influx into outer hair cells opposes cell shortening.

Polyneuropathy associated with IgM monoclonal gammopathy. Immunological and pathological study in 31 patients

Abstract: Quantitative, immunopathological, light and electron microscopic studies of superficial peroneal nerve biopsies from 31 patients with IgM monoclonal gammopathy were carried out. Six patients had Waldenstrom's macroglobulinemia and 25 had IgM monoclonal gammopathy of undetermined significance. Serum samples from 28 of these patients were assayed for anti-myelin-associated glycoprotein (anti-MAG) activity. Anti-MAG activity was found in 25 of the samples. There was a relationship between the widening of some myelin lamellae observed on ultrastructural examination and the serum anti-MAG activity (23 cases). Immunopathological examination showed IgM binding to myelin sheaths in 17 cases.

Distribution and characterization of neuropeptide Y-like immunoreactivity in the brain and pituitary of the goldfish.

Abstract: The distribution of neuropeptide Y (NPY) immunoreactivity has been studied by means of immunocytochemistry and radioimmunoassay in the brain of the goldfish. It was found that NPY had a widespread distribution in the entire brain in particular in the telencephalon, diencephalon, optic tectum and rhombencephalon. In the pituitary gland, positive type-B fibers were observed in the various lobes frequently in direct contact with secretory cells, in particular the gonadotrophs, somatotrophs and MSH (melanocyte-stimulating hormone) secreting cells. When measured by radioimmunoassay, the highest NPY concentrations were found in the pituitary and telencephalon, confirming the results of immunocytochemistry. The displacement curves obtained with serial dilutions of brain extracts were parallel to that of synthetic porcine NPY. Following high performance liquid chromatography, the NPY-like material extracted from goldfish brain co-eluted as a single peak with synthetic porcine NPY. These data demonstrate the presence of an NPY-like substance widely distributed in the goldfish brain. The observation of NPY-immunoreactive fibers in the pituitary gland suggests that, among its other functions, NPY may play a role in the neuroendocrine regulation of pituitary function.

Calcium-activated chloride current in rat vascular smooth muscle cells in short-term primary culture.

Abstract: Isolated cells from rat portal vein smooth muscle in short-term primary culture were studied using patch-clamp technique (whole-cell configuration). In order to study a calcium-activated chloride current, the potassium currents were blocked by intracellular cesium diffusion. Without EGTA in the pipette solution, depolarizing voltage pulses from a holding potential of −70 mV to positive potentials activated an early inward and a late outward current. The latter persisted as a long-lasting inward tail current when the membrane was repolarized to −70 mV. The outward current measured at the end of the pulse and the tail current were blocked by extracellular cobalt, after replacement of external calcium with barium, after removal of external calcium, and when the calcium concentration of the pipette solution was less than 0.5 μM, suggesting that they were calcium-dependent. The tail current decay was voltage sensitive, becoming faster with hyperpolarization. The reversal potential of the calcium-activated current was near the equilibrium potential for chloride ions, and was shifted as predicted by the Nernst equation when the extracellular or intracellular chloride concentration was changed. The calcium-activated current was blocked by adding micromolar concentrations of niflumic acid or millimolar concentrations of DIDS. This effect of compounds known to interfere with chloride channels together with the data on the equilibrium potential for chloride ions indicated above suggested the existence of a calcium-activated chloride current in vascular smooth muscle cells.

Wetting improvement of carbon or silicon carbide by aluminium alloys based on a K2ZrF6 surface treatment: application to composite material casting

Abstract: A surface treatment with aqueous solutions of K2ZrF6 has been carried out to improve, in dramatic manner, the wetting of carbon (or SiC)-base ceramics by liquid light alloys at low temperatures (ie within the 700 to 900°C range) The mechanism which is thought to be responsible for the wetting improvement involves two steps: (i) K2ZrF6 reacts with aluminium with the formation of K3AlF6, other complex fluoride species and intermetallics, (ii) K3AlF6 dissolves the alumina thin layer, coating the liquid light alloy and enables the wetting of the ceramics The mechanism has been worked out from sessile drop experiments, solid state chemistry experiments and composite casting The K2ZrF6 surface treatment appears to be particularly suitable for processing composite materials made of carbon (or SiC) fibrous preforms and aluminium-base matrices according to techniques directly derived from the light alloy foundry

Combinatorial analysis of ramified patterns and computer imagery of trees

Abstract: Herein is presented a new procedural method for generating images of trees. Many other algorithms have already been proposed in the last few years focusing on particle systems, fractals, graftals and L-systems or realistic botanical models. Usually the final visual aspect of the tree depends on the development process leading to this form. Our approach differs from all the previous ones. We begin by defining a certain "measure" of the form of a tree or a branching pattern. This is done by introducing the new concept of ramification matrix of a tree. Then we give an algorithm for generating a random tree having as ramification matrix a given arbitrary stochastic triangular matrix. The geometry of the tree is defined from the combinatorial parameters implied in the analysis of the forms of trees. We obtain a method with powerful control of the final form, simple enough to produce quick designs of trees without loosing in the variety and rendering of the images. We also introduce a new rapid drawing of the leaves. The underlying combinatorics constitute a refinment of some work introduced in hydrogeology in the morphological study of river networks. The concept of ramification matrix has been used very recently in physics in the study of fractal ramified patterns.

Noradrenaline activates a calcium-activated chloride conductance and increases the voltage-dependent calcium current in cultured single cells of rat portal vein.

Abstract: 1. Membrane responses were recorded by a patch pipette technique in cultured cells isolated from rat portal vein. Using the whole-cell mode, pressure ejections of noradrenaline evoked depolarization (current clamp) and inward current (voltage clamp) at membrane potentials of -60 to -70 mV. The noradrenaline-induced response was reversibly blocked by prazosin indicating that the response was mediated by alpha 1-adrenoceptors. 2. The ionic mechanism of the noradrenaline-induced inward current was investigated in potassium-free caesium-containing solutions. Alteration of the chloride equilibrium potential produced similar changes in the reversal potential of the noradrenaline-induced current, indicating that noradrenaline opened chloride-selective channels. There was no evidence implicating sodium or calcium as the charge-carrying ion. 3. Caffeine applied in the bathing solution also induced a transient increase in chloride conductance but the noradrenaline-induced response was lost after application of caffeine. This is interpreted to mean that the increase in chloride conductance induced by noradrenaline and caffeine can occur as a consequence of a rise in intracellular calcium concentration depending on release of calcium from the same intracellular stores. 4. In the presence of caffeine, noradrenaline increased both the voltage-dependent calcium and chloride membrane conductances during application of repetitive depolarizing pulses. It is concluded that in isolated cells of the rat portal vein the depolarization in response to noradrenaline is mediated by an increase in chloride conductance depending on both the calcium release from intracellular stores and the increase of the voltage-dependent calcium current.

An ATP-sensitive conductance in cultured smooth muscle cells from pregnant rat myometrium.

Abstract: The whole cell voltage-clamp technique was used to study the effects of extracellular ATP in cultured smooth muscle cells isolated from pregnant rat myometrium. An inward current was elicited by ATP (IATP) in cells held at -70 mV under voltage clamp. The amplitude of IATP was reduced by estrogen pretreatment and by the end of pregnancy. IATP not only did not undergo any desensitization but showed facilitation. The current-voltage relationship of IATP was linear and reversed close to 0 mV. Changing the sodium electrochemical gradient by decreasing extracellular or intracellular sodium resulted in a linear relationship between the reversal potential of IATP and Na equilibrium potential that, however, differed from the predicted curve for a purely sodium conductance. The conductance activated by ATP was monovalent cation selective with little discrimination between potassium, cesium, and sodium ions. IATP was depressed by divalent cations, and the rank order of potency was Co greater than Mg greater than Ca greater than Ba, suggesting that the free-acid form of ATP was the effective ligand. Adenosine, AMP, and ADP were ineffective in eliciting IATP, whereas ATP gamma S and alpha,beta-methylene ATP were capable of mimicking the effects of ATP, although they were less potent. These results are consistent with the free-acid form of ATP activating a monovalent cation-selective and estrogen-sensitive conductance in myometrium.